1. Technical Field
The present invention relates to an optical writing controller, an image forming apparatus, and an optical writing control method.
2. Background Art
With increasing digitization of information, image processing apparatuses such as printers and facsimiles for outputting digitized information and scanners for digitizing documents have become indispensable. Usually, such image processing apparatuses are configured as multifunctional peripherals (MFPs) that can be used as a printer, a facsimile, a scanner, and a copier including capabilities such as an image pickup capability, an image forming capability, and a communication capability.
Among such image processing apparatuses, electrophotographic image forming apparatuses are generally used for outputting digitized documents. In electrophotographic image forming apparatuses, an electrostatic latent image is formed by exposing a photoconductor, a toner image is formed by developing the electrostatic latent image with a developer such as toner, and a paper printout is output after transferring the toner image onto the paper.
In the electrophotographic image forming apparatuses described above, by matching timing of drawing the electrostatic latent image by exposing the photoconductor to timing of conveying the paper, the image is formed in the correct area on the paper. In tandem-type image forming apparatuses that form color images using multiple photoconductors, timing of exposure of the photoconductors for each color undergoes adjustment processes so that the images developed on the photoconductors for each color are superimposed precisely on each other at the same location. Hereinafter, these adjusting processes are referred to as “alignment correction”.
There are two ways to perforin alignment correction. One is a mechanical adjustment method that physically adjusts the relative positions of the photoconductor and the light source that exposes the photoconductor. The second method is an image processing method that ultimately forms the image at a particular position by adjusting the image to be output in accordance with the extent of image displacement. In the image processing method, by drawing a pattern for correcting and scanning the pattern, the image forming apparatus can obtain design timing, and actual timing that the pattern is actually read. The image forming apparatus performs correction based on the difference between design timing and actual timing so as to form the image on the desired position.